Process oils are hydrocarbon mixtures that boil in the same temperature range as lubricant base oils and are derived from petroleum distillates by solvent extraction. However, unlike lubricant base oils which are rarely employed outside the lubricant field, process oils have a wide range of industrial applications which include using them as a rubber process oil (RPO), ink process oil etc. These oils invariably come in contact with their users who are exposed to the ill effects of their toxicity and other harmful properties. Therefore, to make process oils suitable for these applications, the compositions of process oils have to be carefully controlled during refining.
U.S. Pat. No. 5,034,119 claims bright stock extract and deasphalted oil substantially free from mutagenic activity with mutagencity index less than 1.0. Further the invention was limited to mutagenic index and its relationship with a physical property (boiling point). However, it has not discussed the process for producing rubber process oil and the critical properties required including solvency characteristics such as aniline point and/or hydrocarbon composition and flowability in terms of viscometrics or pour point.
The present invention discloses a method of producing processing oils which contain extremely low concentration of selective polycyclic aromatics. The process comprises of selectively producing vacuum residue with negligible amount of polycyclic aromatics compounds and subsequent deasphalting and extraction followed by suitable blending with heavy alkyl benzene or hydroprocessed base oil or solvent processed base oil or mixture thereof to produce rubber process oils with better solvency characteristics as indicated by aniline point which is less than 70° C. and pour point of less than 27° C.
In U.S. Pat. No. 5,504,135, dewaxed deasphalted oil is used as RPO which has aniline point less than 97° C. However, in the present invention, the process oil is a blend of bright neutral (BN) extract with HAB or hydroprocessed or solvent processed base oil or mixture thereof with aniline point of less than 70° C. U.S. Pat. Nos. 6,248,929 and 6,878,263 discuss about RPO production employing a process with two stage extraction. U.S. Pat. No. 6,146,520 claims selective reextraction process for reducing the mutagenicity Index to less than 1 by using of two different solvents. However the present invention deals with production of vacuum residue containing low carcinogenic PCA compounds followed by solvent extraction and blending with suitable hydrocarbon streams to produce RPO.
In U.S. Pat. No. 6,103,808, high aromatic oil is used as RPO which has aniline point 97° C. or less. However, it does not disclose the selective carcinogenic PCA content. RPO produced in the present invention is having an aniline point less than 70° C. and selective carcinogenic PCA content of less than 10 ppm.
In U.S. Pat. No. 6,399,697, residual oil is mixed with lubricant base oil and then mixture is extracted with a solvent to get a product with low PCA content satisfying the RPO requirements but not disclosing the selective carcinogenic PCA content and Aniline point.
In U.S. Pat. No. 6,410,816, the RPO was produced by mineral oil extraction by using a polar solvent. The extract (40-97%) was blended with base oil (3-60%). In this process deasphalting process was not involved and process conditions are not disclosed. Further in the present invention, selective carcinogenic PCA content is less than 10 ppm.
U.S. Pat. No. 7,972,496 deals with the manufacturing of process oil by mixing extract of deasphalted oil with lubricant base oil with a volume ratio of 95/5 to 60/40. The process oil has aniline point of 90° C. or less with selective carcinogenic PCA content: benzo(a)pyrene content of 1 mass ppm or less; specified aromatic compound content of 10 mass ppm or lower.
The present invention comprises process for producing rubber process oil with selectively producing higher Hildebrand solubility components enriched vacuum residue by selective distillation of Reduced Crude Oil (RCO) to obtain minimum of 10 vol % boiling components in between 490° C. to 550° C.; which leads to higher solubility of rubber process oil with an aniline point of less than 70° C. and higher hildebrand components enriched vacuum residue containing extremely low carcinogenic polycyclic aromatics followed by solvent deasphalting to produce deasphalted oil and then solvent extraction to produce higher Hildebrand solubility components enriched bright neutral extract which then suitably blended with heavy alkyl benzene to produce the process oil having a specified aromatic compound content of 10 mass ppm or lower and benzo(a)pyrene content of 1 mass ppm or less; and further the aniline point of the resultant process oil is 70° C. or less.
European Patent EP1031621 discloses a process for producing process oil by extraction of premixed deasphlated oil with lubricating base oil.
However, the present invention is based on vacuum distillation to selectively produce enriched hildebrand solubility components in vacuum residue which on subsequent processing in deasphalting unit and extraction unit will result in enriched higher soluble process oil with aniline point less than 70° C. as well as benzopyrene content less than 1 ppm.
Chinese Patent CN101691427 discloses a blending of deasphalted oil with naphthenic oil for producing environment-friendly rubber oil having no toxicity and no carcinogenic effects.
However, it does not disclose the critical step of selectively producing enriched hildebrand solubility components in vacuum residue by selective distillation of Reduced Crude Oil (RCO) which leads to higher solubility of rubber process oil with an aniline point of less than 70° C., on subsequent processing in deasphalting and extraction units, with extremely low carcinogenic polycyclic aromatic components.
U.S. Pat. No. 5,034,119 discloses only on mutagenicity index and not disclosed on the solubility and performance indicator such as aniline point less than 70° C.
It does not disclose the critical step of selectively producing enriched hildebrand solubility components in vacuum residue by selective distillation of reduced crude oil (RCO) to obtain minimum of 10% volume recovery boiling components in between 490° C. to 550° C. which leads to higher solubility of rubber process oil with an aniline point of less than 70° C., on subsequent processing in deasphalting and extraction units, with extremely low carcinogenic polycyclic aromatic components.
None of the above disclosures discussed about production of vacuum residue with enriching Hildebrand solubility parameter by produced it with a minimum 10% volume recovery of the boiling components being in the range between 490° C. to 550° C. which increases solubility of rubber process oil with aniline point of less than 70° C., on subsequent processing in deasphalting and extraction units, with extremely low carcinogenic polycyclic aromatic components.